U.S. patent number 5,298,825 [Application Number 07/651,348] was granted by the patent office on 1994-03-29 for single phase electro-magnetic actuator with low obstruction.
This patent grant is currently assigned to Moving Magnet Technologies SA. Invention is credited to Claude Oudet, Daniel Prudham.
United States Patent |
5,298,825 |
Oudet , et al. |
March 29, 1994 |
Single phase electro-magnetic actuator with low obstruction
Abstract
The invention relates to a monophase electromagnetic actuator
which includes a rotor (1) with a cylindrical magnetized section
(5) divided into two N poles transversely magnetized in alternate
directions. The actuator also includes a stator structure
consisting of a first magnetic circuit (2) and a second magnetic
circuit (3), which are joined only by non-magnetic linking parts.
Application: miniature actuators for precision and instrumentation
work.
Inventors: |
Oudet; Claude (Besancon,
FR), Prudham; Daniel (Thise, FR) |
Assignee: |
Moving Magnet Technologies SA
(Besancon, FR)
|
Family
ID: |
9382836 |
Appl.
No.: |
07/651,348 |
Filed: |
February 19, 1991 |
PCT
Filed: |
June 15, 1990 |
PCT No.: |
PCT/FR90/00436 |
371
Date: |
February 19, 1991 |
102(e)
Date: |
February 19, 1991 |
PCT
Pub. No.: |
WO90/16107 |
PCT
Pub. Date: |
December 27, 1990 |
Foreign Application Priority Data
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|
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|
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Jun 16, 1989 [FR] |
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89 08052 |
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Current U.S.
Class: |
310/156.45;
310/156.32; 310/17; 310/186; 310/216.037; 310/216.066; 310/266;
310/96 |
Current CPC
Class: |
H02K
37/125 (20130101); H02K 37/12 (20130101) |
Current International
Class: |
H02K
37/12 (20060101); H02K 001/06 (); H02K 001/27 ();
H02K 021/12 () |
Field of
Search: |
;310/17,156,174,175,254,261,264-268 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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972659 |
|
Mar 1955 |
|
DE |
|
2254897 |
|
Mar 1978 |
|
DE |
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2071121 |
|
Sep 1971 |
|
FR |
|
549308 |
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May 1974 |
|
CH |
|
Primary Examiner: Skudy; R.
Assistant Examiner: Haszko; D. R.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt
Claims
We claim:
1. A single phase electro-magnetic actuator enclosed in a stator
structure and including a rotor arranged inside a brace of said
stator structure, said actuator including an initial magnetic
circuit which includes 2N poles and at least one excitation coil,
and a second magnetic circuit, said magnetic circuits being
executed in a material with high magnetic permeability, the rotor
displaying a thin magnetized section comprised of 2N pairs of poles
which are magnetized across their respective lengths, in staggered
direction, the magnetization being substantially uniform and
extending along a path Y.sub.A that is measured along the travel
path, wherein said initial magnetic circuit is connected to the
second magnetic circuit only by non magnetic linkage parts and
wherein N is an integer value less than .pi.D/8E, E being the
distance measured between said two magnetic circuits and D being
the average diameter of said stator structure.
2. A single phase electro-magnetic actuator according to claim 1,
characterized in that it includes a tubular rotor that is radially
magnetized, and displaying 2N pairs of staggered poles, the ratio
between the thickness E of the brace of said poles and the length Y
of said poles measured on the circumference of the rotor being less
than 0.25, and in that the statoric structure is comprised of said
initial magnetic circuit surrounding the rotor and displaying 2N
polar parts excited by said electrical coils and said second
magnetic circuit comprised of a full cylinder arranged inside the
rotor, the rotor and the two magnetic circuits being coaxial.
3. A single phase electro-magnetic actuator according to claim 2,
characterized in that the pairs of magnetic poles of the rotor are
attached to the second magnetic circuit.
4. A single phased electro-magnetic actuator according to claim 1,
characterized in that the rotor is comprised of a thin disk divided
into 2N angular sectors that are magnetized crosswise in staggered
directions, said rotor being mobile between said initial magnetic
circuit (2) comprised of 2N angular sectors surrounded, for at
least some of them, by said excitation coils and said second
magnetic circuit which is coaxial with the rotor.
5. A single phase electro-magnetic actuator according to claim 4,
characterized in that the thickness of the second magnetic circuit
is at least equal to ##EQU3## where BO represents the induction of
the magnet, B.sub.s at represents the saturation induction inside
the iron, D represents the outer diameter of the magnetized section
of the magnet, d represents the internal diameter of the magnetized
section located inside the armature, and D.sub.s tat corresponds to
the outer diameter of the second magnetic circuit which can be
greater than D.
6. A single phase electro-magnetic actuator according to any one of
claims 4 or 5, characterized in that the second magnetic circuit is
attached to the rotor.
7. A single phase electro-magnetic actuator according to claim 1,
characterized in that at least one of the magnetic circuits
displays along at least one of its polar crests a chamfer or a
tilted edge.
8. A single phase electro-magnetic actuator according to claim 7,
characterized in that each of the sectors of the initial magnetic
circuit displays at least one radial crest which presents a chamfer
that forms an angle with the plane of the rotor ranging between
30.degree. and 60.degree..
9. A single phase electro-magnetic actuator according to claims 7
or 8, characterized in that the width of the chamfer is included
between 1/5 and 1/20 of the length of the developed pole.
10. A single phase electro-magnetic actuator according to claim 1,
characterized in that N is greater than 1, one of the two magnetic
circuits includes at least also one servo-control coil, that is not
traveled by the current and is not influenced by the flow deriving
from the current of the other coils.
11. A single phase electro-magnetic actuator according to claim 1,
characterized in that one of the magnetic elements includes a
servo-control coil.
Description
This invention pertains to a single phase electro-magnetic actuator
which is equipped with a rotor that is arranged inside an armature
of a statoric structure comprised of an initial magnetic circuit
which includes 2N poles and at least one excitation coil, and a
second magnetic circuit. The magnetic circuits are executed with a
material that has high magnetic permeability. The rotor displays a
thin magnetized section which is comprised of 2N pair of thin
magnetized poles crosswise in opposite direction. The magnetization
is nearly uniform and extends along a length Y.sub.A that is
measured according to the displacement path. These types of
actuators are designed especially for rotating actuators or even
control panel indicators. These actuators display the peculiarity
of possessing a large area wherein the force is constant. Hence, it
is possible to execute actuators which possess high reproducibility
and extremely high angular accuracy through servo-control. These
actuators display nevertheless a disadvantage for applications
where advanced miniaturization is sought. Indeed, the constant
force zone only exists, according to what we learn from the state
of the art, when the magnetic circuit is closed. For this to occur,
the initial magnetic circuit and the second magnetic circuit are
united in all instances by a magnetic part which is placed outside
the path traveled by the mobile organ. This magnetic part which
unites the magnetic circuits must display a size that is sufficient
to enable the passage of magnetic flows and therefore embodies an
additional prejudicial cumbersomeness.
The purpose of this invention is to execute a single phase
electro-magnetic actuator which displays the same reproducibility
and angular accuracy qualities, at reduced overall dimensions.
This invention is characterized by the fact that the two magnetic
circuits are connected solely by non magnetic braces, and in that N
is less than ##EQU1## E being the thickness of the distance
armature between the two magnetic circuits and D being the average
diameter of the statoric structure. Under those circumstances, the
applicant was able to execute, surprisingly and contrary to any
lesson derived from the state of the art, an electro-magnetic
actuator in which an extended zone exists at a constant force.
According to an initial implementation mode, the actuator includes
a tubular rotor which is radially magnetized and that displays 2N
pairs of staggered poles, the ratio between the thickness E of the
armature and the length Y of said poles being less than 0.25. The
statoric structure is comprised of an initial magnetic circuit that
surrounds the rotor and displays 2N polar sections which are
excited by electrical coils, and by a second magnetic circuit
comprised of a full cylinder placed inside the rotor, the rotor and
the two magnetic circuits being coaxial, we can execute, by
selecting very low height cylinders, extremely flat indicators or
actuators with very low obstruction.
According to an advantageous variant, the pairs of magnetic poles
of the rotor are attached to the second magnetic circuit. The
second magnetic circuit thus comprises a support for the rotor,
which is fairly fragile, and can support the utilization axis of
the actuator.
According to another implementation mode, the rotor is comprised of
a thin disk which is divided into 2N angular sectors that are
magnetized crosswise in staggered directions, whereby the rotor can
turn around a central axis between an initial magnetic circuit that
is comprised of 2N angular sectors surrounded by excitation coils
and by a second magnetic circuit comprised of a disk that is
coaxial with the rotor and the second magnetic circuit.
Preferably, the thickness of the second magnetic circuit is at
least equal to ##EQU2## BO represents the induction of the magnet,
B.sub.s at represents the saturation induction inside the iron, D
represents the outer diameter of the magnetized part of the magnet,
d represents the internal diameter of the magnetized part located
inside the armature, and D.sub.s tat corresponds to the outer
diameter of the second magnetic circuit which is larger than D. The
second magnetic circuit that is implemented in this fashion allows
for optimal passage of magnetic flows. Therefore, the constant
force zone is the widest possible.
According to a particular implementation mode the second magnetic
circuit is glued onto the rotor. We encompass therefore a second
magnetic-rotor unit that is highly rigid and which can be used
especially as a control panel indicator.
According to a particular implementation mode of this invention, at
least one of the magnetic circuit displays along at least one of
its polar crests a chamfer or a tilted edge. When we say tilted
edge we mean that, in the case of an implementation wherein the
rotor is comprised of a disk, the edge of at least one of the polar
parts forms an angle with a sequent radial line that ranges between
0.degree. and 10.degree., and in the event of a cylindrical type of
implementation the edge of at least one of the polar parts forms an
angle that ranges between 0.degree. and 10.degree. with a secant
generator.
In this particular implementation mode, we master the locking
effect of the rotor in the absence of electrical current, when the
electric current has brought the rotor into a position wherein one
of the edges of the magnetized section cooperates with the chamfer
or the tilted edge. Preferably, the chamfer forms with the plane of
the rotor an angle that ranges from 30.degree. to 60.degree.. The
width of the chamfer is advantageously included between 1/5 and
1/20 of the length of the developed pole.
According to a particular implementation mode, one of the magnetic
poles of the statoric structure is surrounded by a servo-control
coil that issues a control signal.
This invention will be better understood in the description that
follows, or by relying on the drawings where:
FIG. 1 displays a cross sectional view of a rotating actuator
according to the present invention.
FIG. 2 depicts a median cross sectional view of the initial
magnetic circuit of said rotating actuator,
FIG. 3 displays a cross sectional view of a second implementation
mode,
FIG. 4 displays the section of the initial magnetic circuit that
corresponds to that second variant,
FIGS. 5 to 9 display different variants of coiling for a rotating
actuator as displayed in FIG. 4.
The actuator displayed in FIG. 1 includes a cylindrical rotor (1)
and a statoric structure comprised of an initial magnetic circuit
(2) and a second magnetic circuit (3). The rotor (1) is comprised
of a rigid rim (4) on which a thin cylindrical-shaped magnet is
affixed (5). This thin magnet displays six polar sections that are
magnetized crosswise (across their length), in staggered direction.
The rotor (1) is mounted on an axle (6) that is guided by a bearing
(7), for instance a ball bearing. The initial magnetic circuit (2)
is comprised of a part that is executed in a material with very
high magnetic permeability, which is stamped in the shape of a
tray. The initial magnetic circuit displays six polar parts.
Electrical coils (8) are placed around magnetic poles of the
initial magnetic circuit. The second magnetic circuit (3) is
comprised of a disk which is executed in a material that has very
high magnetic permeability. It defines, together with the initial
magnetic circuit (2), an armature (9) in which the magnetized
cylinder circulates (5).
FIG. 2 displays a view of the initial magnetic circuit. We can see
six magnetic poles (10 to 15), as well as electrical coils (8, 16,
17). The coils (8 and 16) are excitation coils whereas the coil
(17) is a servo-control coil that issues an electrical signal to an
electronic circuit. The magnetic pole (11) displays two lateral
crests that are chamfered (18, 19). As can be seen in FIG. 1, the
initial magnetic circuit (2) and the second magnetic circuit (3)
are not joined by magnetic parts but rather by non magnetic linkage
parts (20).
In the implementation mode illustrated in FIG. 3, the rotor is
comprised of a circular magnetized section (21) that is mounted on
a rigid non magnetic rim (22) which cooperates with an axle (23).
The circular magnetized section (21) is divided into two poles that
are magnetized crosswise, in opposite direction. The outer diameter
of the magnetized section placed inside the brace (9). The statoric
structure is comprised of an initial magnetic circuit (2) and a
second magnetic circuit (3). The initial magnetic circuit (2) is
comprised of a cylinder that displays according to two opposite
generators a notch that enables the passage of the excitation coil
(8). The second magnetic circuit (3) is comprised of a full
cylinder which displays, according to two generators, symmetrically
in relation to the notches for the passage of the coil (8), tooling
that avoids the imbalance of the forces being exerted on the
magnetized section (21). The two magnetic circuits (2, 3) are
joined only by the casing (24) that is made of non magnetic
material.
FIG. 4 displays a median cross sectional view of the initial
magnetic circuit. We can see an initial polar section (25)
comprised of an angular sector of a cylinder and a second
symmetrical polar section (26). The coiling (8) is arranged around
the initial polar section (25). A second coiling (22) which is
symmetrical to the initial coiling (8), produces on the polar (26)
a polarity that is opposite to that of the initial pole (25). Each
one of the polar sections (25, 26) displays a lateral edge which is
respectively tilted (28, 29). Those tilted edges make it possible
to adjust the locking force of the rotor when the junction between
the two polar sections of the magnetized section (21) occurs in the
zone wherein a release force reigns.
In the coiling mode displayed in FIG. 5, the coils (8, 27) are
arranged in the crosswise plane, around magnetic circuits
respectively (25, 26). The coiling displays an active section (30)
that extends according to an arc of a circle that follows very
closely the magnetic circuit (25). The linkage takes place along a
linear segment (31) which links the two ends of the active section
(30). That coiling segment such as (31) goes on each side the axle
(23). If the magnetic circuits (25, 26) are extended along a more
significant angular sector, or that the diameter of the axle (23)
prevents the implementation mode displayed in FIG. 5, the coiling
can be carried out as depicted in FIG. 6 or in FIG. 7. In FIG. 6,
the two ends of the active section (31) which forms roughly an arc
of a circle that goes around the axle (23) from the outside. In the
implementation mode displayed in FIG. 7, the linkage section (31)
goes around the axle (23) from the outside.
According to another implementation mode displayed in FIG. (8), the
coiling takes place not in the median plane of the magnetic
circuits but in the crosswise plane. The coiling (8) goes through
the notches that separate the two poles (25, 26) of the magnetic
circuit (2) and goes alternatively through the axle (23) as
depicted in FIG. 9. It is understood that those coiling examples
are provided as examples and do not constitute in any way the
exhaustive compendium of conceivable solutions.
This invention is not at all restricted to the implementation mode
that precedes and it extends on the contrary to all variants.
* * * * *